Electric lamp



May 26, 1936. A. A-THOMA5 2,042,199

ELECTRIC LAMP Filed April 12, 1934 INVENTOR Patented May 26, 1936 UNITED STATES PATENT @FFME ELECTRIC LAMP Application April 12, 1934, Serial No. 720,213

' 3 Claims.

My invention relates to electric lamps of the gaseous-discharge type, like the sodium-vapor lamps which have recently come into use. It is A well known that these lamps require a high operating temperature and the bulb must be heatinsulated to maintain that temperature.

According to my invention, I provide an insulating base von which an electric vapor lamp is mounted, and this base has screwthreads for l0 receiving the screwthreaded end of a heatinsulated glass bell or jacket. The latter may be a double-walled unit evacuated between the Walls .or otherwise made to act as a heat-insulator. The open end of the bell is formed with integral' screwthreads adapted to engage the screwthreads on the base, so that the bell is easily installed and removed.

To hold the lamp firmly on its base, Aespecially in inverted position, I insert a small pad of asbestos or the like between the rounded ends of the lamp and the bell. When the bell is screwed into place, the pad is sufciently compressed to bear against the tip of the lamp and hold it securely on the base.

'Ihe various novel features and practical advantages of my invention will be understood from a description of the accompanying drawing, .in which Fig. 1 is a vertical cross-section view of my new lamp assembly, and

. Fig. 2 shows the parts separated for clearness.

The supporting base I0 is preferably molded in a single piece of suitable insulating material, such as .a condensation product, earthenware, and the like. This base is formed with a .central socket I2, an outer annular shoulder I3, and screwthreads I4. From the socket I2 extends four holes or recesses .I5 for receiving the four contact pins of the lamp, as presently to be explained. A suitable contact piece I6 is located in each hole I5 to engage the inserted contact pin of the lamp, and the members I6 are joined to conductors I'I for properly connecting the lamp in circuit.

The lamp itself, indicated as a whole by L, may be of any practical construction, and is here shown as comprising a glass bulb I8 to provide a sealed chamber containing the electrodes I9, 20 and 2l. The electrode I9 is the cathode, usually a tungsten filament with an electronic coating, and the electrodes 20--2I are the two anodes between which an arc-discharge is maintained to vaporize the metallic sodium or other 55 metal in the bulb. The latter usually contains also a rare gas, like neon, to facilitate the electric discharge. I need say no more about the operation of the lamp, for that is well understood by those skilled in the art, and moreover it forms no part of my invention.

The glass bulb I8 is cemented to a shell 22, preferably molded in one piece of insulating material, like the base I0, and this shell carries four contact pins 22' arranged to enter the holes I5 in the base and rmly engage the spring con- 10 tact pieces I6. The lament I9 is electrically connected to two of the contact pins 22', and each of the other pins is connected to one of the anodes 2li-2l. In the broader aspect of my invention, the electric lamp L may be of any other type and construction requiring heat-insulation.

The lamp L, when mounted on base Ill, is wholly enclosed in a transparent or translucent glass bell indicated as a whole by K, and comprising in this instance a pair of spaced walls 20 23-24. The space 25 between the walls is either evacuated or filled with gas having poor heatconducting properties. The walls 23--24 are blown or molded separately and then fused together along the rim 25', after which the space 25 is exhausted of air through tip 26 or other- Wise. The inner wall 23 is formed with integral screwthreads 23' adapted to engage the screwthreads Ill on base I0, so that the bell K is easily f attached to and removed from the base by sim- 0 ply giving it a few turns.

To assure an air-tight fit between base I0 and bell K, I place a washer or gasket 21 on shoulder I3 of the base, this gasket being preferably of compressible or resilient heat-insulating material, such as asbestos, rubber, fiber, and the like. When the bell is screwed on, the gasket 2l is compressed and seals .the .joint between the bell and the base I0. At the same time, the compressed resilient gasket 21 acts to hold the bell firmly in place and prevents its becoming loose by jarring. The screwthreads 23 may also be formed on the outer wall 24 of the bell, with a corresponding change in the position of the screwthreads I4 on base I0, as will be understood without additional illustration. In some cases the socket I2 may be omitted, the contact holes I5 being then at the top substantially flush with the top of the base I0.

Ordinarily, the pressure of the spring contacts I6 against the contact pins 22 is sufficient to hold the lamp L in position. In some installations, however, the lamp may be used in inverted position, as in street or highway lighting. In such 55 pad 28 is preferably of compressible resilient heatj insulating material like asbestos. If the bulb I8 has an exhaust tip 29 at the center,this tip will sink into the pad and help to centralize the latter K and keep it in place. The pad 28 may also be ring-shaped or of other form. f

'Ihe thickness of the compressible pad 28 is such that, as the bell K is screwed home on the base I0, the pad is compressed sufliciently to push against the lamp and lock it to the base, so that it can not work loose, whether the lamp is upright or inverted. This holding function of the pad 28 is readily appreciated by turning Fig. 1 upside down and Viewing the lamp assembly in inverted position. The pad 28 is too small to cast a shadow, at least not Where the light is needed.

It is known that sodium vapor gives a monochromatic light of yellow or orange-yellow color, which is excellent for out-door lighting. However, for interior illumination this yellow glow is objectionable, and in such instances the heat-insulating bell K is made of colored glass to modify the yellow glare of the sodium vapor. Either one or both of the glass walls 23-24 may be colored for that purpose. Thus, the color or tint incorporated in the glass bell K may be in the red end or the blue end of the spectrum, depending upon the particular kind of light it is desired to produce. Also, for certain purposes it may be desirable to make the outer surface of bell K of frosted or of prismatic glass. It will thus be seen that by changing the optical structure of the heatinsulating bell K, various light effects can be obtained from the enclosed metal-vapor lamp.

Although I have shown and described a speciiic construction, my invention is not limited to the details set forth, but includes such modifications as come within the scope of the appended claims. Furthermore, it is apparent that all thefeatures of my invention need not be embodied in a single device, for some features may be used without others. Y

I claim as my invention:

1. The combination of an insulating block pro- Y vided with a cylindrical projection having exterior screwthreads, there being an annular shoulder at the base of said screwthreads, said block having recesses open at the top and containing kelectric spring terminals, contact pins projecting axially from said lamp and arranged to engage said spring terminals in pressure contact, said pins automatically sliding into and out of engagement with said terminals during the axial movement of the lamp on to and from the block, the pressure engagement between said spring terminals and contact pins holding the lamp against axial displacement, and a double-walled heat-insulating bell of glass supported on said block and enclosing the lamp, the inner wall of said bell having screwthreads engaging the screwthreads on said block, whereby said bell is removably mounted on the block independently of the lamp, the end of said bell abutting against said annular shoulder, which forms a positive stop for the screwing-on movement of the bell.

2. The combination of an insulating blo'ck provided with a central socket which is surrounded by a cylindrical wall having exterior screwthreads, there being an outer annular shoulder at the base of said screwthreads, said block having recesses extending from the bottom of said socket.,

electric terminals in said recesses, an electric lamp having a base portion fitting into said socket and surrounded by said cylindrical wall, Contact pins projecting from the base portion of said lamp and arranged to engage said terminals, said pins automatically sliding into and out of engagementwith said terminals during the axial movement of the lamp onto and from the block, and a doublewalled heat-insulating bell of glass supported on said' block and enclosing the lamp, the inner wall of said bell having screwthreads engaging the screwthreads on said block, whereby said bell is removably mounted on the block independently of the lamp, the end of said bell abutting against said annular shoulder, which forms a positive stop for the screwing-on movement of the bell.

3. The combination of an insulating block having a base portion and a cylindrical extension which is provided with exterior screwthreads, said base portion projecting laterally beyond said extension to form an outer annular shoulder at the base of said screwthreads, a compressible gasket on said outer shoulder, electric terminals carried by said block, an electric lamp removably mounted on said block and having contacts arranged to engage said terminals, and a double-walledxhe'atinsulating bell of glass supported on said block and enclosing the lamp, the inner wall of said bell having screwthreads engaging the screwthreads on said block, whereby said bell is removably mounted on the block independently of the lamp, the end of said bell abutting against-said gasket and compressing it, said gasket forming a. positive stop for the screwing-on movement of thebell.

ADOLPH A. THOMAS. 

